CN107211395A - High-performance non-line-of-sight wireless backhaul frame structure - Google Patents

Abstract

In described examples, a method of operating a wireless communication system includes: communicating with a first wireless transceiver (504) over a first data frame (506) having a first transmit time interval; and communicating with a second wireless transceiver (500) through a second data frame (502) having a second transmission time interval different from the first transmission time interval. Transmitting data between the first data frame (506) and the second data frame (502).

Description

High-performance non-line-of-sight wireless backhaul frame structure

Background technique

The present invention relates generally to wireless communication systems, and more particularly to the transmission of non-line-of-sight (NLOS) backhaul frame structures compatible with Time Division Duplex Long Term Evolution (TD-LTE) Radio Access Networks (RAN).

It is generally understood that a key response to the increase in massive data demands of cellular networks is the deployment of small cells that provide long term evolution connectivity to a smaller number of users than is typically served by macro cells. This allows both providing more transmit/receive resource opportunities to users and offloading the macro network. However, while the technical challenges of Radio Access Networks (RAN) for small cells have been the focus of much standardization work through 3GPP Releases 10 to 12, little attention has been paid to the backhaul counterpart. This is a difficult technical challenge, especially for outdoor small cell deployments where wired backhaul is often not available. This is often due to the unconventional location of small cell sites (such as lampposts, road signs, bus shelters, etc.), where wireless backhaul is the most practical solution.

LTE radio access technology, also known as Evolved Universal Terrestrial Radio Access Network (E-UTRAN), is standardized by a 3GPP working group. OFDMA and SC-FDMA (Single Carrier FDMA) access schemes are selected for DL and UL of E-UTRAN, respectively. Time and frequency multiplexing for user equipment (UE) on Physical Uplink Shared Channel (PUSCH) and Physical Uplink Control Channel (PUCCH), and time and frequency synchronization between UEs ensures optimal cell Inner Orthogonality. The LTE air interface offers the best spectral efficiency and cost trade-off of recent cellular network standards, and as such, has been widely adopted by operators as the only 4G technology for Radio Access Networks (RAN), making it a robust and proven technology. As mentioned above and shown in Figure 2, the trend in RAN topologies is to increase cell density by adding small cells near traditional macro cells. Cellular macro site 200 hosts macro base stations. Macro site 200 also hosts co-located small cell base stations and wireless backhaul hub units (HUs). Macro site 200 has its overlaying small cell sites 204, 205, 207, and 208, each of which also hosts a co-located small cell base station and a wireless backhaul remote unit (RU). Macro site 200 communicates with small cell sites 204 , 205 , 207 and 208 through a point-to-multipoint (P2MP) wireless backhaul system deploying radio links 210 , 211 , 212 , 213 . The base station of macro site 200 communicates directly with UE 206 over RAN link 230 . However, UE 202 communicates directly with the small cell base station of small cell site 204 over RAN access link 220 . The RUs of the small cell site 204 in turn communicate directly with the HUs of the macro cell site 200 over the RAN backhaul link 210 . This can cause significant inter-cell interference between the access link 220 and the backhaul link 210 as well as between the backhaul link 210 and the access link 230 if they both share the same frequency resources, which is a common problem in the RAN. The case where the return frequency reuses 1 scene.

As the backhaul link density increases due to multiple RUs, the difference between the RAN and the backhaul radio channel decreases. This requires a point-to-multipoint backhaul topology as shown in Figure 2. Therefore, conventional wireless backhaul systems, which typically employ single-carrier waveforms by means of time-domain equalization (TDE) techniques at the receiver, are due to their limitations in point-to-point line-of-sight (LOS) channels (e.g., microwave band) operation becomes less practical in these environments. Additionally, this spectrum is already saturated with existing backhaul traffic, so that higher frequencies, such as E-band and V-band, have become very attractive for such links. However, these frequency bands also come with their specific technical challenges (such as high sensitivity to environmental conditions) and require very tight beam pointing and tracking when operating. It is currently not mature enough to provide the level of robustness, flexibility and low cost required for small cell backhaul deployments. Conversely, the similarity between the small cell backhaul and small cell access topology P2MP and the wireless radio channel NLOS naturally leads to the use of very similar air interfaces.

In a wireless system, such as LTE, a base station and a wireless terminal or user equipment (UE) operate as a master-slave pair, respectively, where downlink (DL) and uplink (UL) transmissions are configured or scheduled by the base station. For LTE systems, a TTI is 1 ms long and has the duration of a subframe. Figure 1 shows an LTE TDD UL/DL subframe configuration with different UL and DL allocations to support various UL and DL traffic ratios or to achieve coexistence between different TDD wireless systems. For example, configuration 0 may provide 8 UL subframes (U) including special subframes (S). Configuration 5 may provide 9 DL subframes (D) including special subframes (S).

Several issues are associated with collocated time-division duplex LTE (TD-LTE) RAN and backhaul links at small cell sites, such as achieving a highly integrated and cost-effective solution. These contain RAN and backhaul modems in the same box or even in the same system-on-chip (SoC), which provides self-configurable RAN and backhaul links. Additionally, sparse and expensive spectrum results in sharing the same frequency band for access and backhaul transmission. As such, in-band LTE repeaters are standardized as part of 3GPP Release 10, but are generally inappropriate due to high latency, high block error rate (BLER) and high overhead with 1 ms subframe TTI.

The foregoing methods provide improvements in backhaul transmissions in wireless NLOS environments, but further improvements are possible.

Contents of the invention

In a first embodiment, a method of operating a wireless communication system includes: communicating with a first wireless transceiver via a first data frame having a first transmission time interval; The second data frame of the second transmission time interval is used to communicate with the second wireless transceiver. Data is transferred between the first data frame and the second data frame.

In a second embodiment, a method of operating a wireless communication system includes: using a first frequency resource at a first time through one of an uplink and a downlink through a first data frame having a first transmission time interval while communicating with a first wireless transceiver; and using said first frequency resource at said first time via said one of uplink and downlink via a second data frame having a second transmission time interval Communicate with a second wireless transceiver.

In a third embodiment, a method of operating a wireless communication system includes communicating with a first data frame having a first transmission time interval through one of an uplink and a downlink by a first wireless transceiver with a first data frame having a first transmission time interval. Two wireless transceivers communicate. said first data frame is transmitted at said second wireless transceiver through said one of an uplink and a downlink with a second data frame having a second transmission time interval different from said first transmission time interval. or communicate data, wherein the first data frame and the second data frame use the same carrier frequency.

Description of drawings

Figure 1 is a diagram of a conventional downlink and uplink subframe configuration.

2 is a diagram of a conventional wireless communication system with a cellular macro site hosting a backhaul point-to-multipoint (P2MP) hub unit (HU) serving a remote unit (RU) ) relays communications between the small cell and a plurality of user equipments (UEs).

Figure 3 is a diagram of downlink and uplink subframe configurations according to an example embodiment.

Figure 4 is a diagram of a conventional subset of downlink and uplink subframe configurations.

Figure 5A is a diagram of a subset of downlink and uplink slot configurations according to an example embodiment.

5B is a diagram of a communication system according to an example embodiment.

FIG. 6 is a diagram of a conventional special subframe configuration.

7 is a diagram of downlink (DL) time slots and special time slots according to an example embodiment.

Figure 8 is a detailed diagram of a data frame as in configuration 3 (Figure 4), showing downlink and uplink time slots and special time slots.

FIG. 9 is a detailed diagram of the downlink slots of FIG. 7 .

10 is a diagram showing multiple downlink slot formats according to an example embodiment.

11 is a diagram showing multiple special slot formats, according to an example embodiment.

12 is a diagram showing multiple uplink slot formats according to an example embodiment.

13 is a diagram showing physical downlink shared channel (PDSCH) generation with a single transmit antenna, according to an example embodiment.

14 is a diagram showing physical downlink control channel (PDCCH) generation with a single transmit antenna, according to an example embodiment.

detailed description

Embodiments relate to NLOS time division duplex (TDD) wireless backhaul designs to maximize spectrum reuse. The design utilizes a 0.5ms slot based transmit time interval (TTI) to minimize latency and utilizes 5ms UL and DL frames for compatibility with TD-LTE. Therefore, various UL/DL ratios are compatible with TD-LTE configurations (Fig. 1). This allows for flexible slot assignments for multiple remote units (RUs). A special slot structure is disclosed which contains Synchronization Signal (SS), Physical Broadcast Channel (PBCH), Pilot Signal (PS), Guard Period (GP) and Physical Random Access Channel (PRACH) which will be described in detail. These slot-based features greatly simplify the LTE frame structure, reduce cost and maintain compatibility with TD-LTE. Example embodiments advantageously employ a robust forward error correction (FEC) approach by concatenating a turbo code as an inner code with a Reed-Solomon outer block code that provides a very low block error rate (BLER). Furthermore, embodiments support carrier aggregation with up to four component carriers (CCs) per HU, with dynamic scheduling of multiple RUs with one dynamic allocation per CC. These embodiments also support Semi-Persistent Scheduling (SPS) of small allocations in Frequency Division Multiple Access (FDMA) within time slots for RUs scheduled to transmit high-priority traffic, thereby avoiding time-division redundancy with dynamic scheduling. address (TDMA) associated delay. This combination of TDMA dynamic scheduling and FDMA SPS provides the best performance and least complexity.

Throughout this specification some of the following abbreviations are used.

BLER: block error rate

CQI: Channel Quality Indicator

CRS: Cell Specific Reference Signal

CSI: Channel State Information

CSI-RS: Channel State Information Reference Signal

DCI: Downlink Control Information

DL: downlink

DwPTS: Downlink pilot time slot

eNB: E-UTRAN Node B or base station or evolved Node B

EPDCCH: Enhanced Physical Downlink Control Channel

E-UTRAN: Evolved Universal Terrestrial Radio Access Network

FDD: frequency division duplex

HARQ: Hybrid Automatic Repeat Request

HU: (Backhaul) Hub Unit

ICIC: Inter-Cell Interference Coordination

LTE: Long Term Evolution

MAC: Media Access Control

MIMO: Multiple Input Multiple Output

MCS: Modulation Control Scheme

OFDMA: Orthogonal Frequency Division Multiple Access

PCFICH: Physical Control Format Indicator Channel

PDCCH: Physical Downlink Control Channel

PDSCH: Physical Downlink Shared Channel

PRB: physical resource block

PRACH: physical random access channel

PS: pilot signal

PUCCH: Physical Uplink Control Channel

PUSCH: Physical Uplink Shared Channel

QAM: Quadrature Amplitude Modulation

RAR: Random Access Response

RE: resource element

RI: rank indicator

RRC: Radio Resource Control

RU: (Return) Remote Unit

SC-FDMA: Single Carrier Frequency Division Multiple Access

SPS: semi-persistent scheduling

SRS: Sounding Reference Signal

TB: transport block

TDD: Time Division Duplex

TTI: Transmit Time Interval

UCI: Uplink Control Information

UE: user equipment

UL: uplink

UpPTS: uplink pilot time slot

Figure 3 shows a TDD frame structure with seven UL/DL frame configurations, thus supporting various UL and DL traffic ratios. In one embodiment, this frame structure is used to generate the NLOS backhaul link 210 of FIG. 2 . However, example embodiments may be used to generate any kind of communication link that shares similar coexistence and performance requirements with TD-LTE as an NLOS backhaul link. Therefore, without loss of generality, the frame structure and associated components (slots, channels, etc.) are referred to as "NLOS backhaul" or simply "NLOS" frames, slots, channels, etc.

Referring to FIG. 4, the frame structure of a conventional 10ms TD-LTE frame will be compared with a 5ms TDD frame (FIG. 5A). FIG. 4 is a more detailed view of UL/DL frame configurations 0 to 2 as shown in FIG. 1 . FIG. 5A is a more detailed view of UL/DL frame configurations 1, 3 and 5 as shown in FIG. 3 . The frame of Figure 4 is divided into ten subframes, each subframe has a TTI of 1 ms. Each subframe is further divided into two slots, each slot having a duration of 0.5 ms. Thus, there are twenty slots (0 to 19) in each TD-LTE configuration. A D in a slot indicates that it is a downlink slot. Correspondingly, a U in a slot indicates that it is an uplink slot. Slots 2 and 3 constitute special subframes that allow transition from DL subframes to UL subframes. DwPTS and UpPTS indicate the downlink and uplink parts of a special subframe, respectively.

In comparison, the frames of Figures 3 and 5A have a duration of 5 ms and are based on slots rather than subframes. Each frame has ten (0 to 9) time slots. Each slot has a duration of 0.5 ms. Like the frame of Figure 4, D indicates a downlink slot and U indicates it is an uplink slot. However, in each of the three UL/DL configurations of FIG. 5A , slot 3 of the two frames contains the special slot indicated by S instead of the special slots in slots 2 to 3 and 12 to 13 of FIG. 4 . subframe. This fixed position of the special time slot ensures compatibility with TD-LTE frames. It advantageously allows to always find an NLOS UL/DL configuration that is 100% compatible with any 5ms periodic TD-LTE UL/DL subframe configuration. For example, this prevents NLOS backhaul DL transmissions and TD-LTE RAN UL transmissions from interfering on the access link when they operate on the same frequency. In other words, it advantageously prevents transmitters at the macrocell site 200 of one system from interfering with receivers of the co-located system.

The frame configuration of FIG. 5A has several features in common with the frame configuration of FIG. 4 to ensure compatibility when operating at the same frequency. Both frames have 0.5ms slot duration with seven SC-FDMA symbols and normal cyclic prefix (CP) in each slot. The SC-FDMA symbol duration is the same in each frame. Both frames have the same number of subcarriers for respective 5MHz, 10MHz, 15MHz and 20MHz bandwidths, and both have 15kHz subcarrier spacing. Both frames use the same resource element (RE) definition and support 4, 16 and 64QAM encoding.

The frame configuration of Figure 5A has several unique features. The symbols for each slot are mainly SC-FDMA for both UL and DL. The first SC-FDMA symbol of each slot contains a pilot signal (PS) to improve system delay. A cell-specific synchronization signal (SS) other than PS is included in each frame for cell search and frame boundary detection.

Figure 5B shows a communication system according to an example embodiment. The communication system includes small cell sites 504 and macro cell sites 508 . The small cell site 504 includes a small cell BTS 514 that communicates with the legacy UE 500 over the LTE link 502 according to the frame structure of FIG. 4 . The communication system further includes a backhaul hub unit (HU) 518 , which may be collocated with a macro BTS or base station 520 at a macro cell site 508 . Alternatively, the HU can communicate with the macro BTS through a separate wireless link. Remote unit (RU) 516 is co-located with small cell BTS 514 at small cell site 504 and communicates with HU 518 over backhaul link 506 according to the frame structure of FIG. 5A. Uplink (UL) transmissions from RU 516 to HU 518 are transmitted synchronously with UL transmissions from UE 510 to macro BTS 520 . Synchronous transmissions are aligned at frame boundaries and use the same single-carrier center frequency of the operating bandwidth. UL transmissions from UE 510 to macro BTS 520 are transmitted over LTE link 512 using the frame structure of FIG. 4 . UL transmissions from RU 516 to HU 518 are transmitted over backhaul link 506 using the frame structure of FIG. 5A. Likewise, downlink (DL) transmissions from HU 518 to RU 516 are transmitted synchronously with DL transmissions from macro BTS 520 to UE 510 . Synchronous transmissions are aligned at frame boundaries and use the same single-carrier center frequency of the operating bandwidth. DL transmissions from macro BTS 520 to UE 510 are transmitted over LTE link 512 using the frame structure of FIG. 4 . DL transmissions from HU 518 to RU 516 are transmitted over backhaul link 506 using the frame structure of FIG. 5A.

Figure 6 shows nine (0 to 8) 1 ms TD-LTE special subframe configurations. Figure 7 is a diagram of a 0.5ms NLOS DL backhaul (BH) slot concatenated with a 0.5ms NLOS special slot. NLOS special time slots consist of DwPTS, UpPTS and a guard period to achieve a duration of 0.5 ms. As shown, the UL and DL transmissions of the NLOS backhaul slots are always consistent with those of the TD-LTE slots regardless of the TD-LTE special subframe configuration. Specifically, the DwPTS of the TD-LTE special subframe occurs simultaneously with the DL time slot before the special time slot of the NLOS frame, and overlaps with the DwPTS of the NLOS special time slot. Similarly, the UpPTS of the TD-LTE special subframe occurs simultaneously with the DwPTS of the NLOS special time slot. Therefore, NLOS BH special slots contain the essential features of TD-LTE special subframes to ensure compatibility when operating on the same frequency. Thus, the NLOS frame and special slot structure allow both LTE access and backhaul transmission in UL or DL. Simultaneous transmission occurs during TTIs of the UL or DL slots of Figures 4 to 5A, and at the SC-FDMA symbol level in special subframes and slots of Figures 6 to 7, respectively.

FIG. 8 is a detailed diagram of an NLOS BH frame as shown in UL/DL configuration 3 of FIG. 5 . Here and in the following discussion, the vertical axis of the graph indicates the frequency of the component carrier, and the horizontal axis indicates time, where each slot has a duration of 0.5 ms. For example, a time slot with a bandwidth of 20MHz contains 1200 subcarriers (SC) with a carrier spacing of 15kHz. A frame contains DL slots, special slots and UL slots. Each DL and UL slot has seven corresponding single carrier frequency division multiple access (SC-FDMA) symbols. Each symbol is indicated by a separate column of time slots.

FIG. 9 is a detailed diagram of the downlink slots of FIG. 8 . The DL slots are used to transmit a Physical Downlink Shared Channel (PDSCH) that transfers payload traffic from HU to RU. Besides special slots, it also contains a Physical HARQ Indicator Channel (PHICH) which conveys HARQ ACK/NACK feedback to RUs. A Physical Downlink Control Channel (PDCCH) is also transmitted in this slot. The PDCCH provides PHY control information to RUs for the MCS and MIMO configuration of each RU dynamically scheduled in the slot. The PDCCH also provides PHY control information to the RUs for the MCS and MIMO configuration of each RU that is dynamically scheduled in one or more future UL slots.

To improve latency for high-priority packets, four pairs of spectrum allocations at both ends of the system bandwidth can be assigned to different RUs, where the frequency gap between the two allocation chunks of a pair is the same across the allocation pairs . Resource allocation is done in a Semi-Persistent Scheduling (SPS) method through dedicated messages from higher layers in the PDSCH channel. The size of each SPS allocation pair can be configured depending on expected traffic load patterns. For example, when there is no SPS allocation, no physical resource blocks (PRBs) are allocated for SPS transmission. In case of larger anticipated traffic, two (one on each side of the spectrum) or four (two on each side of the spectrum) PRBs may be allocated. Each RU may have any SPS allocation or multiple adjacent SPS allocations. In one embodiment, all four SPS allocation pairs have the same size. Most of the remaining frequency-time resources in a slot (except PS, PDCCH, PHICH and SPS allocations) are preferably dynamically assigned to a single RU, whose scheduling information is conveyed in the PBCH.

Similar to LTE, to minimize complexity, all allocation sizes are multiples of PRBs (12 subcarriers) and limited to a defined set of sizes. The only exception is for SPS allocations that can take the number of subcarriers closest to the nominal target allocation size (2 or 4 PRBs). This minimizes the waste of guard bands between SPS and PDSCH or PUSCH.

FIG. 10 illustrates various DL slot formats for different component carriers (CCs). A significant improvement over LTE is that the dynamic allocation size of PDSCH varies across SC-FDMA symbols and is adjusted to fit within a control channel that is frequency multiplexed in the same symbol. A transport block carrying user data in a slot is mapped into consecutive SC-FDMA data symbols for that slot. This differs from LTE in that the mapping is done across SC-FDMA symbols of different sizes. This advantageously maximizes the use of all remaining resource elements and improves spectral efficiency. In systems with primary CCs of 10, 15 or 20 MHz, the SPS allocation starts from the second SC-FDMA symbol in the slot. In a system with a primary CC of 5 MHz, SPS allocation starts from the third SC-FDMA symbol in a slot. SPS allocation is only applicable to the primary CC, and no SPS allocation is allocated in the secondary CC. Apart from this difference, DL slots have the same format for primary and secondary CCs.

Figure 11 is a diagram of various special slot formats for different component carriers (CCs) and system bandwidths. RU is UL synchronized to HU. Therefore, a guard time is required at each DL to UL transition. For this purpose, the frame structure reuses the special subframe concept of the TD-LTE frame adapted to a special time slot. The special slots contain the DwPTS in SC-FDMA symbols 0 to 3, the guard period (GP) in SC-FDMA symbols 4 and the UpPTS in SC-FDMA symbols 5 to 6. As previously discussed, the DwPTS and UpPTS transmissions of the NLOS special time slots occur simultaneously with the DwPTS and UpPTS transmissions of the TD-LTE special subframes, thereby preventing the transmitter of one system from interfering with the receiver of another co-located system. UpPTS is an acronym for Physical Random Access Channel (PRACH) and Sounding Reference Signal (SRS) transmission from RUs. PRACH channels may occur every other special time slot, or may have even lower density (eg, 0.1 or 0.01) and may be based on system frame number. Information about the PBCH configuration is broadcast via the PBCH. The PRACH is used at the HU for initial timing adjustment measurements during the initial link setup procedure. SRS is used for CSI estimation and timing offset estimation. The PHY information (MCS and MIMO configuration) of the DwPTS is transmitted in the PDCCH of the previous DL slot. Therefore, no PDCCH is required in special slots. Also for simplicity, special slots do not contain any SPS allocations. SC-FDMA symbol 0 of the DwPTS is a pilot signal (PS) frequency multiplexed with the synchronization signal (SS) in the primary CC. There is no SS in the secondary CC. SC-FDMA symbols 1 to 3 carry the Physical Broadcast Channel (PBCH), and also carry the PDSCH when the system bandwidth is greater than 5 MHz. The PBCH provides system information and RU slot allocation information for the next frame to RUs for all CCs. PBCH occupies the center 300 subcarriers and is multiplexed with PDSCH in FDMA. PBCH is only transmitted on the primary CC. Therefore, on the secondary CC, SC-FDMA symbols 1 to 3 are used to carry PDSCH. SC-FDMA symbol 0 in the primary CC carries a synchronization signal (SS) for cell search/detection and initial synchronization of the primary CC. The SS is assigned the same tone as the PBCH and frequency multiplexed with the PS of SC-FDMA symbol 0.

12 is a diagram of various UL slot formats for different component carriers (CCs). The UL slots are used to transmit a Physical Uplink Shared Channel (PUSCH) that transfers payload traffic from RU to HU. SC-FDMA symbol 0 of PUSCH is a pilot symbol (PS). The Physical Uplink Control Channel (PUCCH) is also transmitted in this slot (in primary CC only). The PUCCH carries HARQ ACK/NACK feedback from RUs, Channel Quality Indicator (CQI), Rank Indicator (RI) and Scheduling Request (SR) for all CCs. PUCCH occupies both edges of the slot bandwidth and is multiplexed with PUSCH in FDMA. PUCCH occupies up to 8 PRBs. Similar to DL slots, SPS allocation is also employed in UL slots of the primary CC. Each RU in each UL slot may be assigned a pair of spectrum allocations at both ends of the system bandwidth. Resource allocation is done with a semi-persistent scheduling (SPS) method. Most of the remaining frequency and time resources in the slot (excluding PS, PUCCH, SPS allocation) are dynamically assigned to a single RU in a TDMA manner, and its scheduling information is transmitted in the PBCH.

13 is a block diagram illustrating physical downlink shared channel (PDSCH) generation for an exemplary wireless system with a single transmit antenna. On the PDSCH, one transport block is transmitted per stream per TTI, and in a 2x2 MIMO system where 2 data streams can be transmitted, 2 transport blocks are transmitted in parallel. A 24-bit CRC1300 is added to each transport block using CRC-24A of LTE. No Cyclic Redundancy Check (CRC) is added to the FEC block (Turbo+RS). There is no turbo code CRC. Early termination is not provided when turbo decoding. One CRC-added transport block corresponds to an integer number of Forward Error Correction (FEC) blocks, where FEC means concatenated Turbo and RS codes. And in one FEC block, there are an integer number of turbo blocks and an integer number of Reed Solomon (RS) blocks 1302 . For example, one transport block after CRC may be mapped to two FEC blocks, and each FEC block may have 3 turbo blocks and 6 RS blocks. The CRC-added transport block is encoded by an RS encoder (eg, RS(255,255-2T)), where T is the error correction capability in bytes of the RS code. Typically a shortened RS code is used, which has the form RS(255-S, 255-2T-S). For example, RS(192,184) and RS(128,122) may be used. In addition, for short allocations (such as SPS allocations), RS code shortening is used as an additional rate matching (RM) scheme in addition to turbo code block rate matching. The RS output block corresponding to one FEC block passes through the byte interleaver 1304 . The interleaved byte symbols are used as input to turbo encoder 1306 . Then turbo coding is applied, such as LTE's turbo code and LTE's RM.

Bit-level scrambling 1308 is applied to the FEC encoded bitstream. For a given RU, different codes may be applied to consecutive FEC blocks, and transport blocks of different layers in the same allocation, but the same code set is repeated across TTIs and cell-specific code hopping is applied to FRC blocks and codewords across slots among. This would provide the benefit of a simple implementation enabling all codes to be precomputed and stored in memory and reused for each TTI.

For each FEC block k in codeword q, bits b ^(q,k) ,.(.0.,) blocks (of which is the number of bits in FEC block k of codeword q transmitted on PDSCH) is scrambled before modulation, resulting in scrambled bits block, which is based on

Wherein the scrambling sequence c ^{(q, k)} (i) is preferably a Gothic sequence known in the art.

The scrambling sequence generator is used at the beginning of each FEC block with Initialization, where n _RU ∈ {0,1,2,...,7} is the RU index in the cell and is the physical layer cell identifier. k' and q' are frequency-hopping FEC block and codeword indices given by:

where n(mod m) means n modulo m, and:

● is the FEC block index;

● is the number of FEC blocks in the transport block associated with codeword q for RU n _RU in slot n _s ;

● is the number of codewords for RU n _RU in slot n _s ;

n _s is the slot index in the frame;

• Up to two codewords can be transmitted in one slot, ie, qε{0,1}. In case of single codeword transmission, q=0.

After bit-level scrambling 1308 , the data stream is symbol-mapped 1310 and applied to a serial-to-parallel converter 1312 . The parallel symbols are converted 1314 to frequency domain symbols by DFT and subcarrier mapped 1316 . The mapped subcarriers are then converted back to the time domain by IFFT 1318 and applied to parallel to serial converter 1320 . A cyclic prefix 1322 is added to the resulting data stream and a half-carrier frequency offset 1324 is applied.

14 is a block diagram illustrating physical downlink control channel (PDCCH) generation for an exemplary wireless system with two transmit antennas. PDCCH generation is functionally similar to the previously described PDSCH generation, so only the different blocks are discussed below. The PDCCH is used to transmit downlink control information (DCI). PDCCH is on a per-link basis, so each dynamic slot resource has its own PDCCH DCI, and each RU must look for the PHY information in the PDCCH DCI that has been allocated by the PBCH to properly decode its downlink PHY channel and properly Transmit uplink PHY channel. Specifically, the PDCCH in each DL slot carries the PHY control information (MCS and MIMO configuration) of the RUs dynamically scheduled in that slot. The PDCCH also carries PHY control information (MCS and MIMO configuration) for dynamically scheduled RUs in one or more future UL slots. Finally, PDCCH indicates potential allocation preemption for both dynamic and SPS allocations through HARQ retransmissions.

A 16-bit CRC is first added to the DCI bits, which is then passed through the RS encoder with the mother code RS (K _RS =255, N _RS =247) using code shortening to accommodate small input payloads. Each such RS block forms a tail-biting convolutional code 1400 (where R=1/3, K=7) and a rate-matched FEC block feeding LTE. The PDCCH MCS is chosen such that the required signal-to-noise ratio (SNR) for PDCCH detection (where FER = 1%) should be 3dB lower than the SNR of the lower MCS of PDSCH and PUSCH such that the PDCCH information is carried in the worst case scenario to RU. The encoded bits are channel interleaved and scrambled 1402 before they are mapped to modulation symbols. QPSK is the preferred modulation format because of its robustness in noisy channels. For 2 transmit antenna or cross-polarized cases, the PDCCH is transmitted in a rank-1 transmission with an Alamodi-type space-frequency block code (SFBC) 1404 .

Each RU uses DL synchronization signal (SS) and pilot signal (PS) for signal and boundary detection, initial carrier frequency offset (CFO) estimation, initial symbol timing and tracking, and channel estimation. The PS sequence is generated in the same way as in LTE. Only one base sequence is available in each base sequence group, making a total of 30 base sequences available regardless of sequence length. Group hopping does not apply. The same base sequence is used for both UL and DL. The base sequence index u ₀ ε{0...29} in use in the cell for PUSCH/PDSCH C/RPS is broadcast in PBCH. The same base sequence is used for both PUCCH and SRS, the index u ₁ ε{0...29} of said sequence is provided by HU to each RU individually through higher layer dedicated signaling in RAR.

Modifications to the described embodiments are possible, and other embodiments are possible, within the scope of the claims. Embodiments may be implemented in software, hardware or a combination of both.

Claims (20)

1. a kind of method for operating wireless communication system, it includes：

Communicated by the first data frame with the first transmission time interval with the first wireless transceiver；And

By the second data frame with the second transmission time interval different from first transmission time interval with second Wireless transceiver communicates.

2. according to the method described in claim 1, it is included between first data frame and second data frame and transmitted Data.

3. according to the method described in claim 1, wherein the duration of second transmission time interval is first hair Penetrate the integral multiple of the duration of time interval.

4. according to the method described in claim 1, wherein the duration of second frame is the duration of first frame Integral multiple.

5. according to the method described in claim 1, wherein first data frame packet contains multiple time slots, each time slot has described the The first symbol in the time of each time slot in one transmission time interval, and wherein the multiple time slot includes pilot signal.

6. according to the method described in claim 1, wherein first data frame packet contains multiple time slots, each time slot has described the One transmission time interval and with corresponding multiple symbols, and the transfer block for wherein having the data for unique user is mapped to The continuous symbol of time slot in the multiple time slot.

7. method according to claim 6, wherein the continuous symbol includes different corresponding allocated sizes.

8. according to the method described in claim 1, wherein first data frame packet contains multiple time slots, each time slot has described the One transmission time interval and with corresponding multiple symbols, and the Part I of wherein each symbol is semi-durable distribution and each symbol Part II is dynamically distributes.

9. method according to claim 8, wherein passing on institute by the specific messages in physical data shared channel PDSCH State semi-durable distribution.

10. according to the method described in claim 1, it includes：

Communicated in the very first time by first data frame with first wireless transceiver；And

The very first time by the 3rd data frame with second transmission time interval with first data frame Synchronously communicated with second wireless transceiver.

11. method according to claim 10, wherein described is up the step of communicated by first data frame One of link and downlink, and it is wherein described logical with second wireless transceiver with first data-frame sync The step of letter is the one in up-link and downlink.

12. method according to claim 10, wherein first data frame and the 3rd data frame use same frequency Rate resource.

13. a kind of method communicated in wireless bandwidth, it includes：

Pass through the first data frame with the first transmission time interval using the first frequency resource of the bandwidth in the very first time Communicated by one of up-link and downlink with the first wireless transceiver；And

Pass through the second number with the second transmission time interval using the second frequency resource of the bandwidth in the very first time Communicated according to frame by the one in up-link and downlink with the second wireless transceiver.

14. a kind of method for operating wireless communication system, it includes：

Up-link and descending chain are passed through by the first wireless transceiver with the first data frame with the first transmission time interval One of road and communicated with the second wireless transceiver,

Wherein described first data frame uses the with the second transmission time interval different from first transmission time interval Two data frames enter row data communication by the one in up-link and downlink with the 3rd wireless transceiver, and

Wherein described first data frame and second data frame use same carrier frequencies.

15. method according to claim 14, wherein the duration of second transmission time interval is described first The integral multiple of the duration of transmission time interval.

16. method according to claim 14, wherein the duration of second frame be first frame it is lasting when Between integral multiple.

17. method according to claim 14, wherein first data frame packet contains multiple time slots, each time slot has described The first symbol in the time of each time slot in first transmission time interval, and wherein the multiple time slot includes pilot signal.

18. method according to claim 14, wherein first data frame packet contains multiple time slots, each time slot has described First transmission time interval and with corresponding multiple symbols, and the transfer block for wherein having the data for unique user is mapped Into the continuous symbol of the time slot in the multiple time slot.

19. method according to claim 14, it includes：

Communicated in the very first time by first data frame with second wireless transceiver；And

Up-link and descending is passed through by the 3rd data frame with second transmission time interval in the very first time The one in link and communicated with the 3rd wireless transceiver.

20. method according to claim 19, wherein it is described the step of communicated by first data frame with it is described The step of being communicated by the 3rd data frame is synchronous.